<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        * {
            margin: 0px;
            padding: 0px;
        }

        body {
            background-image: url(images/1.jpg);
        }

        #mask {
            background-color: rgba(255, 255, 255, 0.3);
            height: 200px;
            text-align: center;
        }

        #mask img {
            width: 200px;
            margin-top: 35px;
            cursor: pointer;

        }
    </style>
</head>

<body>
    <div id="mask">
        <img src="images/1.jpg" alt="">
        <img src="images/2.jpg" alt="">
        <img src="images/3.jpg" alt="">
        <img src="images/4.jpg" alt="">
        <img src="images/5.jpg" alt="">
    </div>
    <script>
        // 获取事件
        var mask = document.getElementById('mask')
        var img = mask.children;
        for (var i = 0; i < img.length; i++) {
            // 点击图片切换body背景图
            img[i].onclick = function () {
                document.body.style.backgroundImage = "url(" + this.src + ")";
            }
        }
    </script>
</body>

</html>